1. Field of the Invention
The system of this invention pertains to systems for the demodulation of phase shift keyed signals. More particularly, the system pertains to the demodulation of coherent phase shift keyed signals. The system of this invention has particular merit when applied to communication systems utilizing a "burst" mode; that is, to systems which transmit data at high data rates for short periods of time followed either by periods of silence or by transmission of data on other frequencies.
Burst mode communication systems utilizing coherent phase shift keyed signals require demodulation systems that rapidly lock-on to the unmodulated phase of the transmitted signal so that only a modest portion of the transmission time is devoted to phase acquisition in order that most of the burst can be allocated to the transmission, reception and demodulation of data.
2. Description of the Prior Art
In the prior art, the local phase reference signal typically is aligned with the unmodulated phase of the received signal by means of a phase locked loop. The phase locked loop normally is implemented by analog means. Compared to the system of this invention the phase-locked loop is a relatively inefficient means for adjusting or correcting the phase of the local reference signal to agree with that of the received signal.